L5. Anatomy of the abdominal viscera

Question 1

From where does the tubular oesophagus run and to where?
What regions does it span across?
How long is it?

Answer 1

Tubular gastrointestinal tract running from the pharynx to the stomach spanning across three regions: the neck, thorax and the abdomen.

it is about 25 cm

Question 2

What is the function of the oesophagus?

Answer 2

conducts food from pharynx to stomach: wave like contractions in peristalsis

Question 3

Describe the path of the oesophagus from the neck to the abdomen

Answer 3

Begins at level of C6 (cricoid cartilage) and descends in midline behind the trachea.

It passes through mediastinum and enters abdomen through T10 muscular part of the diaphragm to the left of midline in the oesophageal hiatus.

Only about 1/2 an inch in the abdomen before entering the right side of the stomach.

Question 4

Describe the importance of the oesophageal hiatus of the diaphragm. Why is this important to the function of the oesphagus?

Answer 4

The right crus surrounds the oesophagus as it passes through. There is a sling from the left crus as well.

Contraction of the diaphragm establishes a pinch mechanism that closes off distal oeseophagus so when the diaphragm squeezes the stomach below, there is a blockage of the area to prevent regurgitation of contents back.

Question 5

Is there a transition or sharp change from oesophageal epithelium to the gastric epithelium? What kind of epithelia are these?

Answer 5

There is a sharp line of demarcation between stratified squamous epithelium of oesophagus down to oesophageal junction where gastric mucosa takes over.

Question 6

What is the narrowing, arterial supply, venous drainage and lymphatic drainage of the cervical region of the oesphagus?

Answer 6

Upper oesophageal sphincter
Supplied by the inferior thyroid artery
Drained by the brachio- cephalic systemic
deep
Drained by cervical nodes

Question 7

What is the narrowing, arterial supply, venous drainage and lymphatic drainage of the thoracic region of the oesphagus?

Answer 7

Narrowing by the aortic arch
oesophageal branches from the abdominal aorta supply it
azygous systemic veins drain it
mediastinal lymph nodes

Question 8

What is the narrowing, arterial supply, venous drainage and lymphatic drainage of the abdominal region of the oesphagus?

Answer 8

narrowing in the diaphragmatic orifice
left gastric coming off the aorta supplies arterial blood
L gastric portal overlaps systemic in venous drainage
pre-aortic nodes

Question 9

What is the porto-systemic abdominal venous system?

Answer 9

There are veins draining into portal system below and the veins into systemic system above the stomach and these anastomose

Question 10

Describe the two types of oesophageal herniation through the oesophageal hiatus

Answer 10

Sliding Hiatal Hernia: The stomach herniates through the hiatus into the thorax. The proximal portion of stomach slides up through hiatus as a result of oesophagus pulling it through - 95% of abnormal protrusions is this

Para-oeosphageal hiatal hernia: rarely, the proximal part of the stomach is adjacent to oesophagus as they are both pushing up through the hiatus

Question 11

Where is the stomach located?

Answer 11

Left upper quadrant, under left dome of the diaphragm

Question 12

Describe the shape of the stomach

Answer 12

Roughly ‘J’ shaped (varies between individuals)

2 opening
2 curvatures: one curve is shorter (lesser curvature) and longer (greater curvature)
2 surfaces (anterior and posterior)

Question 13

Describe the two different openings of the stomach

Answer 13

Oesophageal opening = CARDIAC ORIFICE (not truly at the top of the stomach - on the right border where oesophagus opens into it)

PYLORIC ORIFICE (opening of distal part of the stomach into the duodenum)

Question 14

The stomach is divided into four anatomical component parts. Describe these parts

Answer 14

1. FUNDUS: dome shaped top of the stomach, which projects upwards above and to the left of the cardiac orifice. Usually full of gas (visible on plane chest film)
2. BODY: from the cardiac orifice down. Along the lesser curvature there is a clear notch - where the body of the stomach ends (the ANGULAR NOTCH)
3. PYLORIC ANTRUM: Distal part of stomach is like a funnel: pyloric antrum is the converging part into the pyloric canal.
4. PYLORIC CANAL: most tubular part (distal) of the stomach, thick muscular wall: pyloric sphincter surrounding the lumen (pyloric canal)

Question 15

What is the main role of the pyloric sphincter?

Answer 15

Ensure best mixing of small amounts of food and enzymes of digestion: role of pyloric sphincter. Only small portions of food arrive at the duodenum at any one time (controlled outflow of gastric contents)

Question 16

What are the lesser and greater curvatures tethered to and what by?

Answer 16

The lesser curvature is tethered to the liver (superiorly) by a serous membrane called the serous omentum and from the greater curvature called the greater omentum.

Question 17

Describe the inner lining of the stomach

Answer 17

Interior of the stomach is lined with prominent longitudinal mucosal folds - GASTRIL FOLDS or RUGAE

Closer to the terminal end of the stomach, the rugae increase in prominence

Question 18

There is a very rich blood supply to the stomach, describe those running through the omentums

Answer 18

Gastric vessels: anastomoses along lesser curvature and the greater curvature called the gastroepiploic system

Question 19

What are the three parts of the small intestine?

Answer 19

Duodenum, Jejunum and Ileum

Question 20

Describe the location, length and shape of the duodenum

Answer 20

The Duodenum is 10 inches long.
A C shaped loop that surrounds the head of the pancreas (the tail of pancreas goes to hilum of spleen).
It is centrally located (all but the first inch of the duodenum is retroperitoneal).

Question 21

What is the primary function of the duodenum?

Answer 21

Primary function is digestion and absorption (thus lots of mucosal folds for efficient absorption - high SA)

Question 22

What are the 4 component parts of the duodenum?

Answer 22

Duodenal cap = 2 inches
Vertical part = 3 inches
Transverse part = 4 inches
Duodenojejunal Flexure (DJF) = 1 inch

Question 23

Describe the 4 component parts of the duodenum

Answer 23

1. Duodenal cap (folds) where gastric contents first enter and meet acids. Directed upwards and backwards and coming to settle onto the posterior abdominal wall related to the right crus and psoas (just medial to the right kidney)
2. Vertical part turns down and descends next to the head of the pancreas on the left and on the hilum of the right kidney (descending on the right psoas).
3. Transverse turns and runs horizontal across the posterior abdominal wall. It moves from right psoas to left psoas and crosses in front of the lumbar vertebral column. (across the front of IVC and aorta).
4. Dudenojejunal flexure (DJF) turns up and comes forward on the left psoas. It is tethered by fibrous tissue to left psoas.

Question 24

Where is the most common site for peptic ulcers?

Answer 24

The duodenal cap

Question 25

What is the horizontal line on the cut edge of the vertical (second) part of the duodenum?

Answer 25

transverse of the mesocolon

Question 26

Where and where are the papilla (openings in the second part (vertical) of the duodenum?

Answer 26

On the Postero-medial wall of the duodenum (half way down) there is an opening - papilla MAJOR DUODENAL PAPILLA. The MINOR duodenal papilla is about an inch above it.

Question 27

What are the openings called and what are their functions?

Answer 27

The common bile duct meets pancreatic duct into and these enter the duodenum allowing important enzymes to enter for digestion.

The minor carries a secondary pancreatic duct

Question 28

What extra features can be seen on the transverse section of the duodenum?

Answer 28

Major vessels come off the front of abdominal artery: Superior Mesenteric artery: hook over the front of the transverse duodenum.

There is also a similar cut edge of duodenum (diagonal edge - take off point for mesentery for jejunum and ileum) - all at the level of L3.

Question 29

What makes up the remaining (intraperitoneal) of the small intestine?

Answer 29

About 4-6m left

First 40% is jejunum and the last 60% is ileum.

Question 30

What surrounds the intraperitoneal small intestine? What does this imply?

Answer 30

It is completely surrounded by mesentery = called “The mesentery” and thus it is a very mobile structure.

Neurovascular structures are conducted to the tubular jejunum and ileum by the mesentery from the posterior abdominal wall.

Question 31

Is there a clear demarcation between the jejunum and ileum? What differentiates them from one another? (4 features)

Answer 31

No. There are some techniques used to differentiate them:

Jejunum tends to occupy left upper quadrant and ileum right lower quadrant

The jejunum is larger in diameter (lots of absorption occurs before it reaches ilium) and the jejunum thus also has higher folds

Jejunum has less fat than that of the ileum (you can see the vessels more clearly in the jejunum).

There are fewer archades and long vasorecta for jejunum and opposite for the ileum.

Question 32

What is the arrangement of vessels in the mesentery?

Answer 32

Arcades (proximal loops) coming off the major vessel and from them there are long vertical vessels towards mucosal tubes called vaso recta.

Question 33

At what level does the small intestine become the large intestine?

Answer 33

The whole small intestine ends at the ileoceacal junction

Question 34

What is the ileocecal valve? What is the purpose of this valve?

Answer 34

Mucosa covering a thickened smooth muscle sphincter - controls passage of contents from Small intestine into Large intestine.

Question 35

Describe the relationship of the small intestine with the large intestine

Answer 35

The whole of the small intestine is centrally located in place and the large intestine frames it.
The lumen of the large intestine is much larger than the small

Question 36

Describe the large intestine in terms of length, location and function

Answer 36

It is about 1.5 m long and extends from caecum to anal canal.
Mainly about absorbs water and important ions from intestinal contents and is concerned with the formation of the stool.

Question 37

Describe the formation of the tinia coli

Answer 37

The external longitudinal layer of smooth muscle is discontinuous (unlike the small intestine) forming three long muscle bands which are visible on the surface of the large intestine.

They assist in peristalsis

Question 38

What three features help distinguish the large intestine from the small intestine?

Answer 38

1. Both have an internal circular smooth muscle coat and an external longitudinal coat that runs all the way through the structures.
   The small Intestine: continuous layers. In the large intestine, the internal coat is complete rim but the outer coat creates three discrete long these muscle bands are called tinia coli
2. Because tinia coli are shorter than the mucosal tube (thus gather the tube into HAUSTRA or sacculations) - gathered appearance.
3. Fat tags hanging off the large intestine: OMENTAL APPENDICES or appendices epiploic

Question 39

What is the ceacum? In what region does it sit?

Answer 39

Part of the ILEOCECAL is formed by the caecum. It hangs down below the iloececal JUNCTION at a blind ending pouch. It has the appendix hanging off it.

Question 40

What is the appendix? Where is it (attachment and tip)

Answer 40

Appendix is a narrow tube of variable length (7-10cm) containing lymphoid nodules.

The base is always attached to the blind ending cecum and point of attachment is a constant: where the 3 tinae coli UNITE AT THE BASE OF THE CAECUM.

The site of the tip varies for different people

Question 41

What are the different types of the appendix?

Answer 41

Most common 65% have a retroceocal appendix, tucked up behind the caecum (retrocecal position).

In about 20% of people, it brims over the pelvic brim into the pelvis ( called the pelvic appendix).

Question 42

What are the different parts of the large intestine (colon)?

Answer 42

Cacum
Ascending
Transverse
Descending
Sigmoid
Rectum

Question 43

Describe the path of the ascending colon

Answer 43

To the right hand side of the abdominal cavity. It gets up into the right upper quadrant (under the liver) and has a 90 degree flexure and into the transverse colon: right colic flexure (hepatic flexure).

Question 44

Describe the path of the transverse colon

Answer 44

Transverse colon crosses abdominal cavity from right to left, superiorly. Tucked under the spleen at the left and turns downwards into the descending colon

Question 45

Describe the path of the descending colon and sigmoid colon

Answer 45

Descending colon descends down the left side into the lower left quadrant. Where there is an S shaped loop: sigmoid colon (hangs down in the pelvis) and then comes up and centred into the rectum and colon.

Question 46

Describe the location and appearance of the rectum

Answer 46

Rectum is midline position and the tinea spread out again to become one continuous outer longitudinal coat.